Pretreatement with chronic nicotine and α4* nAChR upregulation correlate with nicotine self-administration. Mice implanted with osmotic pumps (saline (n = 3), 0.4 mg/kg/hr (n = 5) or 2 mg/kg/hr nicotine (n = 4)) for 10 days were subjected to two-bottle choice nicotine self-administration for 5 days following pump removal. A) Pretreatment with nicotine correlates with mean daily dose of self-administered nicotine (R2 = 0.994, p = 0.01, linear regression). Osmotic pump treatment with 0.4 or 2 mg/kg/hr nicotine for 10 days results in a progressively greater amount of α4YFP nAChR upregulation as compared to treatment with 0 mg/kg/hr (% of saline). The α4YFP nAChR upregulation data for the three doses were taken from Nashmi et al.  and show that oral self-administration strongly correlates with upregulation in GABAergic neurons of the VTA (B) (R2 = 0.9999), GABAergic neurons of the substantia nigra pars reticulata (SNR) (C) (R2 = 0.988) and the medial perforant pathway of the hippocampus (D) (R2 = 0.952).